4 files changed, 239 insertions, 4 deletions
diff --git a/internal/timeline/manager.go b/internal/timeline/manager.go
index 95a40aca1..a701756bb 100644
--- a/internal/timeline/manager.go
+++ b/internal/timeline/manager.go
@@ -75,6 +75,14 @@ type Manager interface {
 	// WipeStatusesFromAccountID removes all items by the given accountID from the given timeline.
 	WipeItemsFromAccountID(ctx context.Context, timelineID string, accountID string) error
 
+	// UnprepareItem unprepares/uncaches the prepared version fo the given itemID from the given timelineID.
+	// Use this for cache invalidation when the prepared representation of an item has changed.
+	UnprepareItem(ctx context.Context, timelineID string, itemID string) error
+
+	// UnprepareItemFromAllTimelines unprepares/uncaches the prepared version of the given itemID from all timelines.
+	// Use this for cache invalidation when the prepared representation of an item has changed.
+	UnprepareItemFromAllTimelines(ctx context.Context, itemID string) error
+
 	// Prune manually triggers a prune operation for the given timelineID.
 	Prune(ctx context.Context, timelineID string, desiredPreparedItemsLength int, desiredIndexedItemsLength int) (int, error)
 
@@ -193,7 +201,7 @@ func (m *manager) WipeItemFromAllTimelines(ctx context.Context, itemID string) e
 	})
 
 	if len(errors) > 0 {
-		return gtserror.Newf("one or more errors wiping status %s: %w", itemID, errors.Combine())
+		return gtserror.Newf("error(s) wiping status %s: %w", itemID, errors.Combine())
 	}
 
 	return nil
@@ -204,6 +212,31 @@ func (m *manager) WipeItemsFromAccountID(ctx context.Context, timelineID string,
 	return err
 }
 
+func (m *manager) UnprepareItemFromAllTimelines(ctx context.Context, itemID string) error {
+	errors := gtserror.MultiError{}
+
+	// Work through all timelines held by this
+	// manager, and call Unprepare for each.
+	m.timelines.Range(func(_ any, v any) bool {
+		// nolint:forcetypeassert
+		if err := v.(Timeline).Unprepare(ctx, itemID); err != nil {
+			errors.Append(err)
+		}
+
+		return true // always continue range
+	})
+
+	if len(errors) > 0 {
+		return gtserror.Newf("error(s) unpreparing status %s: %w", itemID, errors.Combine())
+	}
+
+	return nil
+}
+
+func (m *manager) UnprepareItem(ctx context.Context, timelineID string, itemID string) error {
+	return m.getOrCreateTimeline(ctx, timelineID).Unprepare(ctx, itemID)
+}
+
 func (m *manager) Prune(ctx context.Context, timelineID string, desiredPreparedItemsLength int, desiredIndexedItemsLength int) (int, error) {
 	return m.getOrCreateTimeline(ctx, timelineID).Prune(desiredPreparedItemsLength, desiredIndexedItemsLength), nil
 }
diff --git a/internal/timeline/timeline.go b/internal/timeline/timeline.go
index b973a3905..e7c609638 100644
--- a/internal/timeline/timeline.go
+++ b/internal/timeline/timeline.go
@@ -78,12 +78,22 @@ type Timeline interface {
 		INDEXING + PREPARATION FUNCTIONS
 	*/
 
-	// IndexAndPrepareOne puts a item into the timeline at the appropriate place according to its id, and then immediately prepares it.
+	// IndexAndPrepareOne puts a item into the timeline at the appropriate place
+	// according to its id, and then immediately prepares it.
 	//
-	// The returned bool indicates whether or not the item was actually inserted into the timeline. This will be false
-	// if the item is a boost and the original item or another boost of it already exists < boostReinsertionDepth back in the timeline.
+	// The returned bool indicates whether or not the item was actually inserted
+	// into the timeline. This will be false if the item is a boost and the original
+	// item, or a boost of it, already exists recently in the timeline.
 	IndexAndPrepareOne(ctx context.Context, itemID string, boostOfID string, accountID string, boostOfAccountID string) (bool, error)
 
+	// Unprepare clears the prepared version of the given item (and any boosts
+	// thereof) from the timeline, but leaves the indexed version in place.
+	//
+	// This is useful for cache invalidation when the prepared version of the
+	// item has changed for some reason (edits, updates, etc), but the item does
+	// not need to be removed: it will be prepared again next time Get is called.
+	Unprepare(ctx context.Context, itemID string) error
+
 	/*
 		INFO FUNCTIONS
 	*/
diff --git a/internal/timeline/unprepare.go b/internal/timeline/unprepare.go
new file mode 100644
index 000000000..827b274d8
--- /dev/null
+++ b/internal/timeline/unprepare.go
@@ -0,0 +1,50 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package timeline
+
+import (
+	"context"
+)
+
+func (t *timeline) Unprepare(ctx context.Context, itemID string) error {
+	t.Lock()
+	defer t.Unlock()
+
+	if t.items == nil || t.items.data == nil {
+		// Nothing to do.
+		return nil
+	}
+
+	for e := t.items.data.Front(); e != nil; e = e.Next() {
+		entry := e.Value.(*indexedItemsEntry) // nolint:forcetypeassert
+
+		if entry.itemID != itemID && entry.boostOfID != itemID {
+			// Not relevant.
+			continue
+		}
+
+		if entry.prepared == nil {
+			// It's already unprepared (mood).
+			continue
+		}
+
+		entry.prepared = nil // <- eat this up please garbage collector nom nom nom
+	}
+
+	return nil
+}
diff --git a/internal/timeline/unprepare_test.go b/internal/timeline/unprepare_test.go
new file mode 100644
index 000000000..20bef7537
--- /dev/null
+++ b/internal/timeline/unprepare_test.go
@@ -0,0 +1,142 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package timeline_test
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/suite"
+
+	apimodel "github.com/superseriousbusiness/gotosocial/internal/api/model"
+	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
+	"github.com/superseriousbusiness/gotosocial/internal/id"
+)
+
+type UnprepareTestSuite struct {
+	TimelineStandardTestSuite
+}
+
+func (suite *UnprepareTestSuite) TestUnprepareFromFave() {
+	var (
+		ctx         = context.Background()
+		testAccount = suite.testAccounts["local_account_1"]
+		maxID       = ""
+		sinceID     = ""
+		minID       = ""
+		limit       = 1
+		local       = false
+	)
+
+	suite.fillTimeline(testAccount.ID)
+
+	// Get first status from the top (no params).
+	statuses, err := suite.state.Timelines.Home.GetTimeline(
+		ctx,
+		testAccount.ID,
+		maxID,
+		sinceID,
+		minID,
+		limit,
+		local,
+	)
+	if err != nil {
+		suite.FailNow(err.Error())
+	}
+
+	if len(statuses) != 1 {
+		suite.FailNow("couldn't get top status")
+	}
+
+	targetStatus := statuses[0].(*apimodel.Status)
+
+	// Check fave stats of the top status.
+	suite.Equal(0, targetStatus.FavouritesCount)
+	suite.False(targetStatus.Favourited)
+
+	// Fave the top status from testAccount.
+	if err := suite.state.DB.PutStatusFave(ctx, &gtsmodel.StatusFave{
+		ID:              id.NewULID(),
+		AccountID:       testAccount.ID,
+		TargetAccountID: targetStatus.Account.ID,
+		StatusID:        targetStatus.ID,
+		URI:             "https://example.org/some/activity/path",
+	}); err != nil {
+		suite.FailNow(err.Error())
+	}
+
+	// Repeat call to get first status from the top.
+	// Get first status from the top (no params).
+	statuses, err = suite.state.Timelines.Home.GetTimeline(
+		ctx,
+		testAccount.ID,
+		maxID,
+		sinceID,
+		minID,
+		limit,
+		local,
+	)
+	if err != nil {
+		suite.FailNow(err.Error())
+	}
+
+	if len(statuses) != 1 {
+		suite.FailNow("couldn't get top status")
+	}
+
+	targetStatus = statuses[0].(*apimodel.Status)
+
+	// We haven't yet uncached/unprepared the status,
+	// we've only inserted the fave, so counts should
+	// stay the same...
+	suite.Equal(0, targetStatus.FavouritesCount)
+	suite.False(targetStatus.Favourited)
+
+	// Now call unprepare.
+	suite.state.Timelines.Home.UnprepareItemFromAllTimelines(ctx, targetStatus.ID)
+
+	// Now a Get should trigger a fresh prepare of the
+	// target status, and the counts should be updated.
+	// Repeat call to get first status from the top.
+	// Get first status from the top (no params).
+	statuses, err = suite.state.Timelines.Home.GetTimeline(
+		ctx,
+		testAccount.ID,
+		maxID,
+		sinceID,
+		minID,
+		limit,
+		local,
+	)
+	if err != nil {
+		suite.FailNow(err.Error())
+	}
+
+	if len(statuses) != 1 {
+		suite.FailNow("couldn't get top status")
+	}
+
+	targetStatus = statuses[0].(*apimodel.Status)
+
+	suite.Equal(1, targetStatus.FavouritesCount)
+	suite.True(targetStatus.Favourited)
+}
+
+func TestUnprepareTestSuite(t *testing.T) {
+	suite.Run(t, new(UnprepareTestSuite))
+}